Annealing is a heat treatment applied to a material that is intended to alter the material properties such as strength and hardness. Annealing is typically performed by heating the subject material to above the material's re-crystallization temperature, maintaining the selected temperature for a period of time, and then cooling. Annealing is commonly used to improve the material's ductility, relieve internal stresses, refine the material's structure by making it more homogeneous, and improve the material's cold working properties.
Depending on the subject material, following the heating stage, the material may be allowed to cool slowly to ambient conditions, or be cooled more quickly by quenching it in a fluid. Following the annealing process, the material is typically softened sufficiently for further shaping, forming, or stamping.
Stamping of a blank panel into a desired shape may be accomplished through a series of stages. Frequently, the final shape produced by the stamping operation, as well as the rate of production, is limited by the ability of the panel to withstand deformation without developing splits and tears. Annealing can be used during such multi-stage stamping processes to remove strain hardening effects and recover ductility of a partially formed panel, a.k.a., a pre-form, in order to prepare the panel for being formed into the desired final shape.